It is known, for the handling of large or particularly vicious dogs, to use a restraining device in the form of a choke collar wherein a flexible extension of a leash passes through a ring or eye on its free end so as to constitute a tightenable loop engaging the animal's neck. As the animal pulls against the leash, the loop contracts and causes a certain discomfort which will induce the animal to follow the lead of the master.
Such choke collars, however, are not free from drawbacks. On the one hand, their effectiveness is greatest in the area of a dog's neck close to its jaws and diminishes if the collar slips toward the shoulder as it might in the case of a forward-pulling animal. On the other hand, when the leash is allowed to slacken, the collar (unless provided with suitable stop means) may become so loose that the animal may work its head free of the loop, possibly before the master notices that something is amiss.